Pilots and air traffic controllers use the Aeronautical Telecommunication Network (ATN) to exchange datalink messages. It is important for the pilots and controllers to be aware of the operational state of a communication link in a network so they can choose to use an alternate method of communication as needed. Typically, the alternative method of communication is a voice communication. For example, it is important for the pilot to know if a response message sent to the air traffic controller was not received by the air traffic controller due to a change in the operational state of a communication link in the network. Likewise, it is important for the air traffic controller to know if a message sent to the pilot was not received by the pilot due to a change in the operational state of a communication link in the network. The operational state of a communication link in a network can change as the aircraft moves and the coverage patterns for the signal, reflections of the signal and range between the aircraft and the communication network change. Currently, avionics display screens only indicate if the communication management unit (CMU) is communicatively coupled to the ATN with a “CONNECTED” or “DISCONNECTED” message. Likewise, air traffic controller workstation screens only indicate if communication with the communication management unit (CMU) in the aircraft is communicatively coupled to the ATN with a “CONNECTED” or “DISCONNECTED” message.
There is a third transitional operational state between connected and disconnected during which messages cannot be delivered and during which communication can easily be restored. This third state is currently identified as “CONNECTED” or “DISCONNECTED.” This third transitional operational state can last for as long as five minutes, during which time the pilot or air traffic controller may be under the impression that his message is being considered, while in fact, the message may be un-received during the whole transitional time.